Question: Solve for $x$ and $y$ using substitution. ${-2x-2y = 4}$ ${x = y-12}$
Since $x$ has already been solved for, substitute $y-12$ for $x$ in the first equation. ${-2}{(y-12)}{- 2y = 4}$ Simplify and solve for $y$ $-2y+24 - 2y = 4$ $-4y+24 = 4$ $-4y+24{-24} = 4{-24}$ $-4y = -20$ $\dfrac{-4y}{{-4}} = \dfrac{-20}{{-4}}$ ${y = 5}$ Now that you know ${y = 5}$ , plug it back into $\thinspace {x = y-12}\thinspace$ to find $x$ ${x = }{(5)}{ - 12}$ ${x = -7}$ You can also plug ${y = 5}$ into $\thinspace {-2x-2y = 4}\thinspace$ and get the same answer for $x$ : ${-2x - 2}{(5)}{= 4}$ ${x = -7}$